I currently have a 5 gallon square plastic diesel jug that empties in about one minute or less (no gurgling). The top is spring-loaded such that when I flip the jug onto my fuel filler, gravity opens the flow and I just stand there while it empties into the tank. I can't find these online so I suspect they're not made any more, but it works great. I had two, but one got loose in the back of my truck and a corner got cracked (quite the mess).
For people stuck with the 5 gallon can, I got
two of these and they're fantastic (they're sold on Amazon too but on their website they're cheaper especially if you buy 2 or 4; I have no connection with the seller other than having bought two cans from them) - they open & close very easily and positively and it's very simple to put a spout on them.
They came with high-flow spouts which are most likely not CARB approved (and other sellers sell them separately), but they shipped them to me in CA anyways. When I asked them why they didn't ship the CARB approved spouts, they told me that they supply the CHP (CA Highway Patrol) and the CHP won't accept the CARB spouts...
I bought an old 60 gallon aluminum tank (yet to be cleaned and mounted). I'm hoping eventually to get to this task and put it on a pallet and fork it on top of my container; hopefully that's enough of a gravity drop and not too far for the hose & spout I bought from TSC, or I'll have to build a shorter support.
I haven't set it up yet mostly because my tractor fuel tank is at waist level on the side, so refilling with a can is easy, and with 3x5 gallons reserve and a ~9.5 gallon tank I typically don't come near completely running out of fuel before I remember to refill a couple cans, but I'd feel a lot better if I did have a bigger reserve, especially with my truck that can use it if necessary.